DM3730CUS 512MB LPDDR

Andrew5821

Other Parts Discussed in Thread: DM3730

Our current DM3730CUS prototype uses 1 256MB 32-bit LPDDR400 chip. This has worked well. Now I need to double the amount. I was planning on just adding the same 32-bit part on the second chip select (cs1) and second clock enable (cke1). Part is MT46H64M32LFCX-5 IT:B. We went ahead and routed Data, Address, etc on a T network with each branch of the network being length matched per the datasheet. Termination resistors are right next to the DM3730 and so are the DRAM chips, Overall trace lengths are around 2.7 inch at most, so this is pretty compact. The layout guidelines don't really talk about a second chip on the other chip select so I'm assuming we did the right thing? For example, Figure 6-22 isn't too helpful because it looks like this figure is for two 16-bit devices. Can someone please confirm we did the right thing here for layout and DRAM compatibility.

Thanks

over 12 years ago

0 Cvetolin Shulev-XID over 12 years ago

TI__Guru 65405 points

Hi Andrew,

The DM3730 processor supports 1 x16 LPDDR device is used for 16 bit LPDDR memory system or 1x32 or 2x16 LPDDR devices are used for a 32-bit LPDDR memory system. Is is not guaranteed the proper work of 2x32 bit LPDDR devices and you could try this at your risk.

For more details you can look at the Table 6-13. and the notes below in the DM3730 processor data sheet at the link:

http://www.ti.com/lit/ds/symlink/dm3730.pdf

Tsvetolin Shulev

0 Andrew5821 over 12 years ago in reply to Cvetolin Shulev-XID

Genius 4565 points

Thank you for the response. So why even have two chip selects then?

0 Andrew5821 over 12 years ago in reply to Andrew5821

Genius 4565 points

It seems that TI gives conflicting information between the TRM and the Datasheet (sprs685d). The TRM on pages 2227 -2228 says that the memory configurations in the table are valid per chip select. Could someone at TI please verify?

0 Cvetolin Shulev-XID over 12 years ago in reply to Andrew5821

TI__Guru 65405 points

Hi Andrew,

Sorry for my misunderstood. The description in the TRM is right and my previous post:

"The DM3730 processor supports 1 x16 LPDDR device is used for 16 bit LPDDR memory system or 1x32 or 2x16 LPDDR devices are used for a 32-bit LPDDR memory system."

refers to configuration per chip select.

Tsvetolin Shulev

0 BrandonAzbell over 12 years ago in reply to Andrew5821

TI__Guru 64920 points

Andrew5821,

The fundamental limitation is that the SDRC interface of the DM37xx is that it can only support 2 loads on the interface. Please see a wiki article regarding the SDRC which indicates this. The article is for a device that is sibling of the DM37xx.

http://processors.wiki.ti.com/index.php/AM3715/03_SDRC_Subsystem

0 Chien Lim over 12 years ago in reply to BrandonAzbell

Prodigy 10 points

Hi,

In the topic about LPDDR, our manufacturer heard from TI in Taipei that we should not use DM3730 as the LPDDR is going EOL.

If that is the case, what can I use if all I need is: (1) Camera Interface, (2) DSP, and (3) USB.

Thanks,

Chien

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DM3730CUS 512MB LPDDR